The present invention relates to a resin sealed semiconductor device, that is, a resin sealed electronic device and a method of fabricating the resin sealed electronic device and an ignition coil device for an internal combustion engine using the above resin sealed electronic device.
Various proposals to improve reliability of the resin sealed electronic devices have been made by reducing strains produced in the sealing resin in order to suppress occurrence of cracks.
Japanese Patent Application Laid-Open No.10-107182 discloses a resin sealed semiconductor device. The resin sealed semiconductor device in which electrodes formed on a board are electrically connected to a semiconductor chip through bumps, and a gap between the board and the semiconductor chip is filled with a sealing resin and the surrounding of the semiconductor chip is covered with the sealing resin, wherein when a height of the peripheral portion of the sealing resin covering the surrounding of the semiconductor chip from bottom end surface of the semiconductor chip is (b) and a distance between the outer peripheral edge of the peripheral portion and the bottom edge of the semiconductor chip in a plane being flush with the bottom end surface of the semiconductor chip is (a), an average value of (a/b) is smaller than 2; and the sealing resin is a resin material of an epoxy group composed of an epoxy resin and spherical particles made of a low thermal expansion inorganic material having a thermal expansion coefficient lower than that of the epoxy resin; and the sealing resin contains the inorganic material within the range of 50 to 80 weight % to the total weight.
Further, Japanese Patent Application Laid-Open No.9-246300 discloses a method of fabricating a semiconductor device. The method of fabricating a semiconductor device is one in which a chip is arranged on a board opposite to each other with a gap between them, and the gap between the chips and the board is filled with a lower layer side sealing resin, and the whole chip is covered with a upper layer side sealing resin, wherein the method of fabricating the semiconductor device comprises the first process of injecting a thermosetting resin before setting into the gap between the chip and the board; the second process of making the resin bring in a semi-set condition; the third process of disposing a thermosetting resin before setting so as to cover the whole chip; and the fourth process of completely setting the both laminated resins.
In the case where a flip chip is contained inside a conventional resin sealed electric device as described in Japanese Patent Application Laid-Open No.10-107182, an under filler material is initially injected and filled under the flip chip and then the under filler material is set, and after that the circuit board portion including the flip chip is sealed with a resin through transfer molding. Therefore, before sealing the whole circuit with the resin, there is the process of injecting, filling and setting of the under filler material. Most of liquid under filler materials have linear expansion coefficients near that of the solder in order to secure the reliability of the soldered portions, and such liquid under filler materials need to be stored at a low temperature and are heated up to room temperature when they are used. However, the pot-life of the liquid under filler material is short, and accordingly management of the liquid under filler material is troublesome because it needs to be run out within the pot-life period. Further, particularly, in a case where the size of flip chip is small and the bump height is low, it takes a very long time to inject and fill the under filler material, and to inject and fill the under filler material into the under portion of the bumps and to set the under filler material.
On the other hand, since the reliability of the electronic device may be deteriorated when the transfer molding resin is not bonded to the under filler material, control of setting the resin must be performed in order to improve bonding by making the under filler material bring in a semi-setting condition as described in Japanese Patent Application Laid-Open No.9-246300.